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Plasma metformin concentration as a determinant of metabolic response in adults with type 1 diabetes: a 1-year prospective observational study

Bekier M, Uruska A, Michalak M, Czyrski A, Miętkiewska-Dolecka M, Szkutnik-Fiedler D

Frontiers in pharmacology, 2026

26 participants · 1 citation

Abstract

Background: Metformin is commonly used as adjunctive therapy in adults with type 1 diabetes (T1DM), although evidence regarding its long-term metabolic effects remains inconsistent. To assess the metabolic effects of adjunctive metformin therapy in adults with type 1 diabetes (T1DM) over a 12-month period, using advanced markers of metabolic control, including time in range (TIR), estimated glucose disposal rate (eGDR), and monitoring of metformin plasma concentrations.

Methods: This single-center, observational study included 26 adults with T1DM treated with extended-release metformin (500-2000 mg/day). Metformin plasma concentrations were measured at baseline and at 5 time points up to 12 months using a validated UPLC-MS/MS method. Glycemic control (TIR), insulin dose, anthropometric parameters, lipid profile, visceral adiposity index (VAI), and eGDR were assessed. Participants were grouped by median metformin concentration.

Results: Interindividual variability in metformin plasma concentrations was significant. Adjunctive metformin therapy was associated with significant reductions in LDL cholesterol, non-HDL cholesterol, and VAI. A significant transient improvement in eGDR was observed after 6 months of therapy, followed by partial attenuation at 12 months. A significant interaction between metformin concentration subgroup and time was observed for TIR (p = 0.0151), with descriptively greater improvement in participants with higher metformin concentrations. No…

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